httprepo: use separate handlers for HTTP and HTTPS
This is needed to keep the code in keepalive.py from sharing
the same connection between HTTP and HTTPS.
52ce0d6bc375 explains why we were using a single handler.
This should fix
issue892.
move __del__ from httprepository to basehttphandler
This should prevent the next patch from reopening an issue fixed by
0d94e4a3ddb4.